Artificial culture conditions induce irreversible deformations in Hyalosynedra toxoneides

The cell deformation in two Hyalosynedra toxoneides (Castracane) comb. nov. strains (AQ9 and AQ10) isolated from Renting, Taiwan was characterized. Their morphology displayed patterns consistent with the generic characteristics of the genus Hyalosynedra. In particular, the valve is covered by a bilayer pore plate. These two strains vary in their stria arrangement with known Hyalosynedra, especially in the striae arrangement. The 18S rDNA molecular analysis was also consistent with our morphological analysis. Using NJ. MP and ML evolutionary tree constructs, our strains were found to be in the same branch with Synedra toxoneides and Hyalosynedra sp. with bootstrap support; thus, we make the new combination, Hyalosynedra toxoneides and assign this name to two isolated strains, AQ9 and AQ10. We also found they have closer links with a sister group of the Thalassionemataceae than with other Synedra-type diatoms. In addition, artificial culture conditions induced deformations in the cell wall; a serpentine shape in AQ9 and a more fixed S-shape in AQ10. From this we concluded that the diatom valve probably follows an original genetic model which is conserved.